Quality of Air? That’s as Murky as Western Sky

A dust storm in Phoenix in July. Scientists say it is hard to gauge the cleanliness of Western air.

DENVER — Oh say, can you see across the Grand Canyon? Not as well as you used to on some days.

The question of how clean the air is in the American West has never been an easy one to answer, strange to say. And now scientists say it is getting harder, with implications that ripple out in surprising ways, from the kitchen faucets of Los Angeles to public health clinics in canyon-land Utah to the economics of tourism.

It is at least partly about dust, something that has been entwined with Western life for a long time, and now appears to be getting worse.

But now a new and even more complicated chapter appears to be unfolding, researchers in many different fields say. From off-road vehicle use, which has in some places replaced the clumping trod of the old cattle herds, to drought’s impact on plants with their soil-anchoring roots, more dust appears to be up and moving.

And scientists say they are also understanding for the first time the deep connections between the dust’s main source — a vast high-desert region called the Colorado Plateau, which stretches through four states and is home to national parks like the Grand Canyon and Arches — and the economic, environmental and demographic life in cities and suburbs far removed.

In the last few years, winter dust storms on the high peaks of the Rocky Mountains in Colorado have sharply increased in number, affecting the rate of melting snows into the Colorado River, a main source of water for agriculture and for the drinking supply for more than 20 million people. Of 65 so-called dust-on-snow events since 2003, when tracking began, 32 have struck in just the last three years, according to the Center for Snow and Avalanche Studies, a nonprofit research group based in Silverton, Colo. Dust can accelerate how fast snow melts because it absorbs heat.

“It’s not a mysterious process,” said Chris Landry, the organization’s executive director. “Anybody who has thrown coal dust on their driveway or sidewalk to melt it down knows the theory.”